As continuing increase of high density cabinets in the IDC internet data center room, devices' integration level increases, and so does their processing ability. However, power consumption of the devices also increases, resulting in more heat generated by the devices inside the cabinet. According to statistics, current cabinet servers in huge IDC rooms produce a lot of heat and basically operate 8760 h for a whole year. For a room that does not utilize fresh air, cooling is required for the whole year, which results in a huge power consumption by the air conditioning system, which accounts for about 40%-50% of the total power consumption in the data room.
Conventional ways for air supply in a data room comprise air supply through an air passage in the bottom plate, air supply through separated hot and cold passages, and air supply by cooling in the whole room. However, this mode can no longer meet the cooling requirement for high density cabinets in a modernized computer room, and causes problems related to local overheating, high power consumption, and too high energy consumption by air conditioners in the room, and loud noise. In the meantime, precise air conditioning in the room requires repeated humidification and dehumidification operations, or providing a specialized dehumidifier to perform humidity and dew-point control in the room, so as to ensure that no condensation occurs inside the devices, which results in decrease in efficiency of the air conditioning system, and increase in power consumption. If the heat dissipation problem is not well solved, safety operation of the devices in the room will be greatly affected. Therefore, it is important in the air conditioning industry and in the data room operating industry how to effectively reduce power consumption of the air conditioning system inside the computer room while meeting requirements of devices.
From the energy saving view, currently there exists a solution where outdoor air is directly introduced indoor for cooling the room. This solution provides advantages of high cooling efficiency, low initial investment and low power consumption. However, the introduction of outdoor cold air makes it hard to ensure the cleanliness and humidity of the indoor air, which brings safety risks and requires lots of maintenance in future operations. In addition, there also exists a solution where air-air cellular heat exchanger is used to indirectly exchange heat between hot air in hot pipes and outdoor cold air, so as to reduce temperature inside the room. Its advantage is that no outdoor air is introduced when using an outdoor cold source, which does not affect the cleanliness and humidity of the air inside the room. However, its disadvantage is that it requires relatively high initial investment, complex structures for the heat exchanger, is easy to be blocked, and requires regular cleaning and lots of maintenance.
As the development of server techniques, servers with high power and high heat density are being more and more utilized. This development is irreversible. Currently, the maximum operating power of a single cabinet of some of the users in this industry has reached about 10-15 kW. However, due to the limitation in heat dissipation efficiency of air cooling, it is hard for a high power server to be utilized under more than 15 kW per cabinet.
Liquid heat dissipation is a heat dissipation solution developed in recent years which is most efficient and most advanced. Its principle is to introduce a liquid heat exchange medium directly into a server with liquid cooling function, and carries out the heat generated by the main heat generating element—the chip (CPU) which accounts for 70-80% of the total heat generated in the server. A liquid heat dissipation solution theoretically provides a power per cabinet of even more than 50 kW.
However, this heat dissipation solution currently only exists in university laboratories and very few corporations for internal small-scale study, and has not yet been practicalized. One of the main reasons is that this kind of servers for liquid heat dissipation requires a liquid distributing system inside its cabinet, which requires specialized custom designing for the server cabinet. However, cabinet manufactures normally only provide standardized production, and have not mastered key technologies related to designing for a liquid distributing system, therefore, they cannot provide server users with a cabinet having inside a liquid distributing system. Especially for the upgrade of old computer rooms, in order to utilize a liquid heat dissipation solution, all the cabinets have to be replaced with cabinets having a liquid distributing system, which requires a very large amount of work and a very high cost, greatly affecting the development and popularization of liquid cooling technique.
In addition, only 70-80% of the heat in the server can be taken out by the liquid cooling system, remaining 20-30% of the heat to be handled by an auxiliary cooling device. For a high density application in a liquid cooling server having a power up to 50 kW per cabinet, each cabinet requires the auxiliary cooling device to handle more than 10-15 kW heat (20-30% of the total power). If traditional air cooling is still used in the auxiliary cooling device, local overheating may occur very easily in the cabinet, affecting the life of the elements in the server, which is also a problem that cannot be ignored in the development and popularization of high density liquid cooling servers.
A server cabinet has been disclosed by the Chinese application No. 201010261284.1 with the title of “Server cabinet and liquid cooling system thereof”, which comprises a housing, a server provided inside the housing, and a liquid cooling system. The housing is provided with a heat conducting plate adjacent to the server. The liquid cooling system comprises a refrigerator outside the housing, and a pipe thermally connecting the heat conducting plate with the refrigerator. Heat generated due to operation of the server forms a heat flow in the housing which is cooled at the heat conducting plate. The pipe extends outside the housing and is respective connected with two opposite ends of the refrigerator, so as to transfer the heat absorbed from the server by the heat conducting plate to the refrigerator to perform heat exchanging. Although liquid heat dissipation is also used in this patent application, the heat in the server cannot entirely be taken out by the liquid cooling system. Therefore, there still exist problems such as local overheating and short life.
A server cabinet cooling system has been disclosed by the Chinese application No. 201210545675.5 with the title of “A server cabinet cooling system”, which comprises a liquid cooling box provided inside the cabinet, a water cooling device inside the cabinet, an air cooling device inside the cabinet, first liquid reservoir, and an outer cooling system. The liquid cooling box comprises a fin heat exchanger, a plate heat exchanger and a first pump integrated inside one box. The hot water side of the plate heat exchanger, the first pump, the first liquid reservoir, and the water cooling device are connected to form a first circulation loop by a pipe. The outer cooling system, the air cooling device, the fin heat exchanger, and the plate heat exchanger are connected to form a second circulation loop by a pipe. In this patent application, the heat of the first circulation loop is taken away by the second circulation loop. However, the cooling device in the first circulation loop performs heat conduction to the air inside the whole cabinet, instead of performing heat conduction directly to the heat generating chips in the server, which results in a low cooling efficiency and poor effect. In addition, the first circulation loop is provided with the first pump which generates much heat during its operation. Thus a specialized heat exchanger is required to transfer the heat accumulated during operation of the first pump, which undoubtedly brings a burden to the system and thus further reduces the cooling efficiency of the system.
A control method of a server cabinet cooling system with a hot pipe secondary refrigerant circulation loop has been disclosed by the Chinese application No. 201410511550.X with the title of “A control method of a server cabinet cooling system with a hot pipe secondary refrigerant circulation loop”, which comprises a room unit, a refrigerant supplying and returning unit, and a controlling system. The refrigerant supplying and returning system comprises a cooling unit and a circulating power unit, wherein the circulating power unit is connected with the room unit by a water supplying pipe or a water returning pie and connected with the cooling unit by an outdoor air outlet pipe or an outdoor liquid returning pipe, and the cooling unit and the circulating power unit are both connected with the controlling system. The room unit comprises a cabinet, one or more cooling fans, multiple servers, multiple hot pipe heat dissipaters, and multiple hot pipe heat exchange devices. The cooling fans, the servers, the hot pipe heat dissipaters and the hot pipe heat exchange devices are all arranged inside the cabinet, wherein the hot pipe heat dissipaters are closely attached on the servers, the hot pipe heat exchange devices are connected with the hot pipe heat dissipaters, the hot pipe heat exchange devices are connected with the water supplying pipe of the cabinet by a water supplying pipe and connected with the water returning pipe of the cabinet by a water returning pipe. In this patent application, the hot pipe heat dissipaters are only attached on the servers, and are not directing cooling main heat generating elements. In addition, heat exchange between the two circulation loops is performed by an intermediate heat exchanger in this system, which certainly results in a heat transfer efficiency lower than that in direct heat exchange. In addition, only heat dissipation for main heat generating elements (CPU) are considered in this patent application, but heat dissipation for other heat generating elements (such as memory and hard disk) are not considered. Therefore, the heat dissipation solution provided in this patent application is not enough.